Just yesterday I upgraded from Performance to Blast internet. Since upgrading, my download speeds have noticeably increased as expected. For whatever reason though my upload speed has tanked. It has been over 24 hours since the upgrade from Performance to Blast was done remotely. I did make sure to power cycle my modem and router. I also tested by plugging my PC directly into my modem bypassing my router altogether but I am still receiving extremely slow upload speeds.

Previously on Performance, I was receiving 30 Mbps download and approximately 6 Mbps upload while testing on my iPhone 6 Plus using the SpeedTest.net app. I would also see these speeds on other devices as well.

Since upgrading though, I am receiving download speeds of approximately 105 Mbps. My upload speed now is around 1 Mbps or even a little less. However, last night after midnight, I ran a speed test and did receive upload speeds of nearly 12 Mbps as I would expect on Blast. However right now as I write this, my upload speeds are still terrible. I know some may blame the time of the day when I tested as being a factor, but back when I was on the Performance plan, my speeds would pretty much always be a consistent 30 Mbps down and 6 Mbps up regardless of time of day.

I did not change any of my equipment or hardware since the upgrade. I am using a Motorola DOCSIS 3.0 SB6120 modem and a ASUS RT-N66U (running Asuswrt-Merlin firmware) wireless router.

I do not see anything abnormal in the modem or routers logs.

I'm guessing this is an issue on Comcast's end, but just thought I'd post here to see if anyone has any other suggestions or tips.

Re: Upgraded from Performance to Blast. Abysmal Upload Speeds

Just a brief update that I just got off with Comcast technical support chat.

They did the basic troubleshooting including sending a refresh signal to the modem, and having me power cycle my modem and router. As expected though, my upload speed did not get any better.

They scheduled a technician to come out and take a look outside of the house to see what is going on. Hopefully they can figure out what is happening.

I still find it odd that my upload speed was always consistent back when I was on the performance plan, but has now actually gotten worse since changing speed tiers. Then again, I have no idea how things work in regards to cable internet once it leaves the house.

Re: Upgraded from Performance to Blast. Abysmal Upload Speeds

I decided to check with a friend of mine who is also on the Blast tier and he too is experiencing very slow upload speeds. He lives about a mile away from where I am. So I'm guessing this isn't just a problem isolated to me and is happening somewhere else. Not sure if it affecting all Comcast HSI users in my area or just those on the Blast tier.

Re: Upgraded from Performance to Blast. Abysmal Upload Speeds

An update.

When I got home from work yesterday, I had a message to call Comcast advanced technical support. Before I called, I ran several speed tests from different devices, and my upload speeds were excellent, near 12 Mbps. So I assume the problem was resolved elsewhere. After I called back, the person on the phone had me confirm/test to make sure everything seemed normal, and I told him that everything looked great. He then asked if I wanted to cancel the technician visit today, 6/4, which I did tell him to cancel.

Unfortunately only a couple of hours later, the upload speed became terrible again, under 1 Mbps up. Even the download speed seemed to decrease.

I did check with my friend/neighbor again and they too are experiencing the slow speeds once again, as I did have them test their speeds when I noticed that mine had initially improved.

Upload Speeds Randomly Changing from 12 Mbps to 1 Mbps or Less

I later learned, in regards to that slow upload speed issue, that it wasn't just exclusive to me, but also was happening to a friend who lived about a mile away from me with Comcast as well. In the end, the upload issue was not directly with my house or his house, by was happening elsewhere. I'm not sure what Comcast did to fix it or what the actual issue was.

Unfortunately, my friend has moved away, so I am unable to have them test now when I am experiencing my upload speed dropping.

My specs are the same as the post above but to recap:Modem: Motorola SB6120Router: ASUS RT-N66R (RT-N66U)Internet Plan: Blast 105 (from speed tests, I more often than not, see download speeds of 135 Mbps and upload speeds of 12 Mbps) (I upgraded from the performance plan in June 2015)

Modem upstream power levels are at: 45 dBmV 44 dBmV 44 dBmV

Sites I typically use to run speed tests:http://www.speedtest.net/ (I sometimes test using different servers (Ashburn, VA and New York, NY) and not always the recommended one (Plainfield, NJ) (I also sometimes use the app in iOS as well.)http://testmy.net/ (I usually test using the Washington, DC and the New York, NY servers)http://speedof.me/

CURRENT ISSUE DESCRIPTION BELOW-------------------------------------Recently I built myself a new computer and have started streaming to Twitch using OBS. I have my settings in OBS set to use 3.5 Mbps when streaming. I am streaming at 720p 60fps. My computer is directly connected to my router via Ethernet cable and is on a local gigabit connection. For the Twitch server I am streaming to, I pick either New York, NY or Ashburn, VA.

What I noticed happening is that OBS will show me when I start dropping frames. When I noticed this happening, I decided to troubleshoot the best I could. This is when I learned that, when I notice a lot of frames dropping, that my upload speed from Comcast has dropped.

I thought that I may be getting throttled, but I don't think this is the case.

When I notice the dropped frames, I tested my internet speed using the first 3 URLs I listed above, and noticed that my upload speeds changed from the usual 12 Mbps to around 2 Mbps to 3 Mbps, if not slower.

I also ran speed tests on other devices on my network, to make sure the problem wasn't exclusive to my PC or NIC, and found that the slow upload speeds are not exclusive to just the PC.

Eventually, (I don't have an exact time frame, maybe 10-20 minutes), my upload speeds will return to normal, without me having to do anything to my modem or router.

It's worth noting that on Tuesday, February 9, 2016, I streamed for 4 hours and 30 minutes (from about 6:00 PM to 10:30 PM) and dropped 0 frames during that time. So I have to guess my upload speed remained normal/consistent. Last night, Wednesday, February 10, 2016, I streamed for about 1 hour and 30 minutes (from about 9:00 PM to 10:30 PM), and for the majority of my stream, I had 0 dropped frames. Towards the end of my stream though, the last 20 minutes or so, I started dropping frames, and decided to quit the stream and run some speed tests, only to learn that my upload speed had dropped again, hence the dropped frames. -------------------------------------END OF CURRENT ISSUE DESCRIPTION

While I've ran plenty of other speed tests in between the ones listed above, any other time I ran a speed test, both download and upload speeds were normal. The ones above were the times I ran a test and noticed slow upload speeds.

I'm not sure if anyone has any suggestions or has experienced anything similar. The only thing I do know is that when I was having upload speed issues last June, was that it didn't seem exclusive to just my home, and that the issue seemed to be elsewhere.

Re: Upload Speeds Randomly Changing from 12 Mbps to 1 Mbps or Less

I wanted to provide a few other updates as well in regards to my current issue with the random/intermittent but consistent slow upload speeds.

Last week, when I was still on my old SB6120, I was messaging a Comcast engineer who checked my signals and capacity on my segment. They told me the upstream capacity for my node looks great and that my signals also looked good.

I did update my router's firmware last week as well, but this did not make any difference to the upload speed issue.

Shortly after upgrading my modem to the SB6190 from the SB6120, I still encountered the slow upload speeds. During this time, I plugged my new modem directly into my computer, and I still was experiencing the slow upload speeds. I thought this would be a good idea to rule out my router causing any issues. Eventually, as it did previously when I was on the SB6120, after some time and without any intervention on my part, my upload speed returned to normal.

I also did a chat with Comcast technical support last night and they too checked my signals and capacity and did not see any issues. They told me monitor and see if the issue happens again, which I'm sure it will.

I do realize that is it difficult to troubleshoot this issue since it does happen randomly, but still consistently enough to me, for it to be aggravating.

Re: Upload Speeds Randomly Changing from 12 Mbps to 1 Mbps or Less

I know this was from Feb, its now July. But I wanted to see if you ever found out what was the issue or if you're still having this issue? I stream as well and have done everything and more that you have done. I too have had less than 2 upstream, most of the time between 6pm-5am. my download remains the same and all my db levels are perfect. Had a tech out and didn't find the issue. Another tech will be out in 2 days, I've been nonstop trying to figure this out around the clock. I have the sb6141, we(comcast tech and I) have tested other modems and no change.

My OBS has over 40% dropped frames and I consistantly sit at 1400 kb/s or lower. It's been an ongoing issue for 2 weeks now, before I was running 20 mb/s upstream vs my 0.5 - 1.5 mb/s now.

Re: Upload Speeds Randomly Changing from 12 Mbps to 1 Mbps or Less

Please post your own new topic about our issue if you wish. Year old dead thread now being closed.

I am not a Comcast Employee. I am a Customer Expert volunteering my time to help other customers here in the Forums.We ask that you post publicly so people with similar questions may benefit from the conversation.Was your question answered? Mark the post as Best Answer!